1. Field of the Invention
The present invention relates to a method of preparing a cyclic olefin polymer using a metal catalyst complex, and a polymer prepared using the method. More particularly, the present invention relates to a method of preparing a cyclic olefin addition polymer using a metal catalyst complex including an N-heterocyclic carbene (NHC) ligand, and a polymer prepared using the method.
2. Description of the Related Art
Cyclic olefin polymers, which are polymers composed of cyclic olefin monomers such as norbornene, have better transparency, heat resistance, and chemical resistance, and much lower birefringence and hygroscopicity, compared with conventional olefin-based polymers, and thus, can be widely applied as optical materials for CDs, DVDs, or POFs (Plastic Optical Fibers), information and electronic materials for capacitor films or low dielectrics, medical materials for low-absorbent syringes or blister packagings, etc. In particular, polynorbornenes are noncrystalline polymers which have a high glass transition temperature, a high refractive index, and a low dielectric constant, and thus, have been widely used as electronic materials. Much research about polynorbornenes has been actively done by Heitz et al [(a) T. F. A. Haselwander, W. Heitz, S. A. Krugel, J. H. Wendorff, Macromolecules, 1997, 30, 534. (b) T. F. A. Haselwander, W. Heitz, S. A. Krugel, J. H. Wendorff, Macromol. Chem, Phys. 1996, 197, 3435.].
Norbornene monomers can be easily polymerized since they can be easily converted to polymers in the presence of various palladium or nickel complexes and cocatalysts [Ni: (a) WO95 14048A1 (1995), B. F. Goodrich Co., invs.: B. L. Goodall, G. M. Benedikt, L. H. Mcintosh III, D. A. Barnes; Chem. Abstr. 1995, 123, 341322p. (b) EP 445755 A2 (1991), Idemitsu Kosan Co. Ltd., invs. : H. Maezawa, J. Aiura, S. Asahi. Chem. Abstr 1991, 115, 256943g., Pd: (a) U.S. Pat. No. 3,330,815 (1967), Union Carbide Corp., invs. : J. E. McKeon, P. S. Starcher; Chem. Abstr. 1967, 67, 64884g. (b) F. Hojabri, M. M. Mohaddes, A. Talab, Polymer 1976, 17, 710].
However, norbornene monomers having a saturated hydrocarbon ring structure are hardly soluble in organic solvents, and are inferior in adsorptivity to metals, etc. which is required for use of them as electronic materials, thereby limiting the applications of the norbornene monomers. In view of these problems, extensive research has been actively conducted. In order to easily change the physical properties of polymers, for example, to improve the solubility of conventional polynorbornenes, and to provide new physical properties to the polynorbornenes, a method of modifying the chemical structures of norbornene monomers and a method of incorporating new functional groups to norbornene monomers have been proposed. In particular, low solubility in organic solvents of norbornene monomers can be easily overcome by incorporating polar functional groups to the norbornene monomers. Alternatively, research about norborene/ethane copolymerization [(a) H. Cherdron, M. J. Brekner, F. Osan, Angew. Makromol. Chem. 1994, 223, 121. (b) M. Arndt, I. Beulich, Macromol. Chem. Phys. 1998, 199, 1221] or norbornene/functionalized norbornene copolymerization [T. F. A. Haselwander, W. Heitz, M. Maskos, Macromol, Rapid. Commun. 1997, 198, 3963] has been actively conducted. These copolymerization reactions can also contribute to better adsorption of copolymers with other objects.
A catalyst mainly used in the preparation of cyclic olefin polymers was a catalyst complex including, as a cocatalyst, an organic phosphine compound that has been used as a σ electron donor ligand. For example, U.S. Pat. No. 6,455,650 discloses a method of polymerizing a functionalized norbornene-based monomer in the presence of a catalyst complex represented by [(R′)zM(L′)x(L″)y]b[WCA]d where phosphine and a hydrocarbyl (e.g., allyl)-containing hydrocarbon are used as ligands. Sen, et al. [Organometallics 2001, Vol. 20, 2802-2812] reported ester norbornene polymerization catalyzed by [(1,5-cyclooctadiene)(CH3)Pd(Cl)] and cocatalyzed by phosphine (PPh3) and [Na]+[B(3,5-(CF3)2C6H3)4]−.
However, separate addition of a phosphine cocatalyst requires a separate step for converting a catalyst precursor to an activated catalyst and significantly reduces catalyst activity in the presence of a polar functional group-containing cyclic olefin monomer.
Recently, preparation of polar functional group-containing norbornene polymers in the presence of phosphonium compounds as cocatalysts have been disclosed in Korean Patent Laid-Open Publication Nos. 2004-0052612 and 2004-0074307.
For synthesis of an aromatic olefin monomer (e.g.: stilbene), ER 0721953B1 discloses a metal catalyst complex including an N-heterocyclic carbene (NHC) ligand instead of a phosphine ligand. However, the working examples of this patent document disclose that the NHC ligand is mainly substituted simply by an alkyl group or a sulfonated alkyl group.
As one of various methods for improving the performance of metal catalysts, a method of partially substituting ligands with various functional groups has been proposed. The method is considering an electronic effect of a ligand. The improvement of the performance of catalysts through adjustment of the electronic effect of a ligand has been reported in several documents. For example, an improvement of catalyst activity through a ligand electronic effect adjusted by changing a substituent of a Grubbs ruthenium carbene catalyst ligand has been reported [(a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18-29. (b) Love, J. A.; Sanford, M. S.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc. 2003, 125, 10103-10109].
With respect to catalysts used in polymer synthesis, Waymouth found that the electronic effect of a ligand plays an important role in adjusting the stereoselectivity of propylene polymerization in the presence of a zirconocene catalyst [Lin, S.; Hauptman, E.; Lal, T. K.; Waymouth, R. M.; Quan, R. W.; Ernst, A. B. J. Mol. Catal. A: Chem. 1998, 136, 23-33]. Coates reported that when carbon dioxide (CO2) and epoxide are copolymerized in the presence of a β-diiminate zinc alkoxide catalyst, partial substitution of a ligand with a cyano group enables to significantly increase a polymerization rate [Moore, D. R.; Cheng, M.; Lobkovsky, E. B.; Coates, G. W. Angew. Chem., Int. Ed. 2002, 41, 2599-2602].
However, until now, there was no report about a further improvement in performance of metal catalysts through a ligand electronic effect achieved by partially substituting a NHC ligand with various functional groups affecting ligand electron density. Therefore, it is necessary to develop a new polymerization method of preparing a cyclic olefin polymer using a metal catalyst complex that shows better performance by substituting a NHC ligand with various functional groups.